1. Field of the Invention
The present invention relates to a function driving apparatus, a function driving method, and a computer-readable storage medium having a function driving program stored thereon, which are applicable to a portable device.
2. Description of the Related Art
Conventionally, portable electronic devices including a display device have been known, such as a wristwatch, a portable telephone, a smartphone, and a media player. These electronic devices are often provided with a light source such as a backlight for clarity of display in the display device and for ease of viewability. However, since most of the portable electronic devices are driven by a battery incorporated therein, there is a problem in that exhaustion of the battery is severe by driving the light source, whereby the driving time of the electronic device is shortened and the convenience is degraded. To solve these problems, various technologies have been developed and put to practical use in order to achieve both convenience of the portable electronic device and long life of the battery.
For example, Japanese Patent Application Laid-Open (Kokai) Publication No. 09-257965 describes a wristwatch having a tilt switch and an acceleration switch incorporated therein, where a display panel (an EL panel) is lit up when the wristwatch is tilted at a predetermined angle based on outputs from both of these switches. Also, Japanese Patent Application Laid-Open (Kokai) Publication No. 2011-142497 describes a technique in which a backlight is lit up when a portable terminal is tilted at a predetermined angle based on an output from an acceleration sensor incorporated in the portable terminal.
However, in Japanese Patent Application Laid-Open (Kokai) Publication No. 09-257965, the tilt switch and the acceleration switch are both required to be provided to control the display panel to light up, and therefore there is a problem in that the number of components is increased, whereby the size of the electronic device and the product cost are increased.
On the other hand, in Japanese Patent Application Laid-Open (Kokai) Publication No. 2011-142497, the backlight is controlled to light up only with the output from the acceleration sensor. In this case, processing for detecting the tilt of the portable terminal in a stationary state (or substantially in a stationary state) is performed. Normally, the portable electronic device (portable terminal) is always carried by a user or mounted on a human body for use. For this reason, for example, when the user is performing continuous motions or workout such as walking or running, an accurate tilt of the portable terminal cannot be detected and the backlight may erroneously operate in the scheme disclosed in Japanese Patent Application Laid-Open (Kokai) Publication No. 2011-142497. Moreover, to prevent this erroneous operation, the user has to once suspend or stop the motions or workout to cause the portable terminal to stay still, by which the convenience is degraded.